bone bigger than armature
The easiest way is to select your Meta-Rig and go into Edit Mode - select all the bones and scale to your Mesh size. You could also do the same thing in Object mode, with one additional step - applying the scale with CTRLA

This answers your question - below is just extra stuff that may be helpful...

The scale should by default go towards the Median point - which is that little orange dot which identifies the root of your object. At the moment your Mesh object and Meta-Rig object have different positions for the Median point. Best practice is to get them aligned. You can do this by selecting your Meta-Rig in Object mode and ShiftS Cursor to Selected. With the position established now select your Mesh in Object mode and move the Median point to the same location...



Now you can return to your Meta-Rig in Edit mode and start positioning the bones...